It is well known to process the surface of a substrate such as glass by using silane-based, germanium-based, tin-based, titanium-based or zirconium-based molecules, for example, in the case of manufacturing a glass fiber reinforced plastic (FRP) by improving the adhesiveness between the glass fibers and the plastics.
The conventional methods will be explained employing examples using silane-based molecules as follows. The conventional methods using germanium-based, tin-based, titanium-based or zirconium-based molecules may use the same method as in the example using silane-based molecules explained below.
Silane-based molecules used in a first conventional example are chlorosilane-based molecules. Other halosilane molecules such as bromine silane-based molecules or the like have the same functions as chlorosilane-based molecules. A solution is prepared by dissolving in alcohol silane-based molecules having monochlorosilane groups, dichlorosilane groups or trichlorosilane groups as a material for forming a coating film. A method of dipping a substrate into the solution, a method of applying the solution to a substrate, a method of spraying the solution on a substrate or the like is used as a method for forming a coating film on a substrate using the solution. A coating film made up of chlorosilane-based molecules is formed using any one of such methods, although there are differences in thickness and in uniformity of the film in each method.
Next, a second conventional example will be explained as follows. Molecules used here are alkoxysilane-based molecules. Isocyanate-based molecules have the same functions as the alkoxysilane-based molecules. A solution is prepared by dissolving silane-based molecules having monoalkoxysilane groups, dialkoxysilane groups or trialkoxysilane groups as a material for forming a coating film in hydrocarbon molecules. A method of dipping a substrate into the solution, a method of applying the solution to a substrate, a method of spraying the solution on a substrate or the like is used as a method for forming a coating film on a substrate using the solution. A coating film made up of alkoxysilane-based molecules is formed using any one of such methods, although there are differences in thickness and in uniformity of the film in each method. Then, the substrate on which a film has been formed is fired, wherein a temperature of 100.degree. C. and a time period of one hour usually are employed as standard conditions. As a result, a siloxane bond is formed by a dehydration reaction, a dealcoholization reaction or the like between alkoxy groups of the alkoxysilane-based molecules and hydroxyl groups of the alkoxysilane-based molecules already hydrolyzed, between alkoxy groups of the alkoxysilane-based molecules, between hydroxyl groups of the alkoxysilane-based molecules already hydrolyzed, between hydroxyl groups on the surface of the substrate and alkoxy groups of the alkoxysilane-based molecules, or between hydroxyl groups on the surface of the substrate and hydroxyl groups of the alkoxysilane-based molecules already hydrolyzed, thus forming a coating film.
As a third conventional example, a solution is prepared by dissolving chlorosilane-based molecules in a silicone oil. The solution prepared here is applied to a substrate by using the same method as in the first example, and thus forming a coating film.
However, in the case of using the method for forming a coating film in the first conventional example mentioned above, the chlorosilane groups of the chlorosilane-based molecules react with the alcohol in which the chlorosilane groups dissolve, and alkoxysilane groups are formed. The alkoxysilane groups are changed to silane groups having high reactivity, and the chlorosilane-based molecules, alkoxy-based molecules changed from the chlorosilane-based molecules, silanol-based molecules changed further from the alkoxy-based molecules and the like react with each other. As a result, a thick coating film having a non-uniform thickness is formed. Furthermore, a tight chemically bonded film should be inherently formed by the reaction between hydroxyl groups on the surface of the substrate such as glass or the like and the chlorosilane groups or the alkoxy groups. However, the film formed here is not tightly bonded to the substrate, since the number of reactive chlorosilane groups, alkoxysilane groups and silanol groups which are included in the material molecules is overwhelmingly more than the number of the hydroxyl groups exposed on the surface of the substrate, and the great majority of the molecules therefore react with each other. Similarly, in the second conventional example, a coating film similar to that of the first conventional example is formed, since a reaction occurs between the alkoxysilane-based molecules and the silanol-based molecules changed from the alkoxysilane-based molecules. In the third conventional example, the chlorosilane-based molecules are not changed to silanol-based molecules, since the solution is composed of silicone oil and oils, which does not include water. However, the atmosphere in the dissolving process is not a dry atmosphere, so that a little water content comes to be included during the dissolving process. The water molecules are changed to silanol-based molecules by reacting gradually with the chlorosilane-based molecules, thus forming an oligomer. As a result, as a storage time of the material becomes longer, a coating film formed becomes similar to that of the first and second conventional examples.
In the first, second and third conventional examples, the atmosphere is not controlled so as to be a dry atmosphere during the production of a chemically bonding material, the preparation of the material into a coating solution composition and the storage of the composition. Therefore, the method according to the first, second and third conventional examples mentioned above is disadvantageous in that the silane-based molecules are deactivated and do not react with the surface of a substrate such as glass or the like.